Ninety metres of stone that made the site possible
The Kamisaibara Power Station Penstock and Main Building Retaining Walls are stone retaining walls of 1930 in the Taruhara district of Kamisaibara, Kagamino, Okayama Prefecture, and they were listed as a Registered Tangible Cultural Property on 29 November 2006. They run to 90 metres in total and fall into two groups with two different jobs.
The first group flanks the penstock that connects the powerhouse with the head tank above it. These are straight walls, one on either side of the pipe, holding the cut slope back from the pipeline. The second group divides the ground on the west and north sides of the powerhouse, forming the terrace the building occupies.
Both are stone masonry. In a valley with almost no level ground, this is the work that had to be done before anything could be built, and it is the part that visitors normally walk past without registering. The Agency for Cultural Affairs record notes that the walls remain in good condition and close to their original form.
Why the walls were registered
Registration number 33-0148 belongs to the Kamisaibara Power Station Penstock and Main Building Retaining Walls, the last of nine structures of this station accepted on 29 November 2006 under the criterion that they contribute to the historic landscape of the country.
The register, created in 1996, covers works still in service and asks an owner to notify the authorities before major alteration rather than to leave a structure untouched. A Registered Tangible Cultural Property can therefore go on carrying load, which these walls have done for close to a century. Okayama Prefecture records all nine of these structures as facilities in current use.
Registering site works alongside a building is unusual enough to be worth pausing over. A powerhouse is easy to recognise as architecture; a retaining wall reads as ground. The listing treats the terrace and the building as one act of construction, which is how the engineers of 1930 would have understood it. The same view produced registrations for stone retaining walls at the neighbouring Iri and Heisakubara stations.
What to look at
Follow the walls beside the penstock uphill and watch how the coursing adjusts. A retaining wall on a slope has to change its batter as the ground steepens, and the masons handled that by altering the size of the blocks and the run of the joints rather than by stepping the wall. The result reads as a continuous surface even though the geometry beneath it is changing constantly.
At the powerhouse, look at the junction between the wall and the building. The two are separate constructions doing separate things, and the small gap between the stone and the concrete is not a defect. It lets the wall settle at its own rate without dragging the structure with it.
Ninety metres is a considerable length for site works of this date, and walking the line of the Kamisaibara Power Station Penstock and Main Building Retaining Walls gives a better sense of the scale of the 1930 earthworks than any of the water structures do. What you are reading is the shape of the hillside before the engineers arrived, recorded in the negative.
Visiting
These walls are part of an operating power station. No admission is charged, no opening hours are published, and the walls stand within the fenced site.
Okayama Prefecture asks anyone wanting to view the facilities to arrange it in advance with the Tsuyama Power Office of Chugoku Electric Power, on 0868-27-0275. Photography is best raised on the same call.
The powerhouse and its terrace are in Taruhara, in Kamisaibara, the northernmost district of Kagamino, near the Tottori border and on the line of National Route 179 between Tsuyama and Ningyo Pass. By public transport, take the JR Kishin Line to Tsuyama Station or Inno-sho Station, then the Chutetsu Hokubu Bus service towards Okutsu Onsen and Ishigoshi; Kagamino town publishes the timetables. The walls are best seen from the valley road, where the full run up the slope is visible at once.
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Q&A
- What are the Kamisaibara Power Station Penstock and Main Building Retaining Walls?
- Two groups of stone retaining walls of 1930. One pair runs straight up the slope on either side of the penstock between the powerhouse and the head tank; the other divides the ground on the west and north sides of the powerhouse.
- How long are the Kamisaibara Power Station Penstock and Main Building Retaining Walls?
- 90 metres in total. All of it is stone masonry, and the Agency for Cultural Affairs record notes that it survives close to its original form.
- Why would retaining walls be registered as cultural property?
- Because the terrace and the building are a single act of construction. Almost no level ground exists in this valley, so the walls were the work that made the station possible at all.
- Can I walk up beside the penstock?
- No. The slope is inside the operator's fence and is steep and wooded. Viewing of the plant is arranged through the Tsuyama Power Office of Chugoku Electric Power on 0868-27-0275.
- Are similar walls registered elsewhere on the upper Yoshii River?
- Yes. Stone retaining walls form part of the registered groups at the Iri station of 1920 and the Heisakubara station of 1928, both in Kagamino.
Basic Information
| Name | Kamisaibara Power Station Penstock and Main Building Retaining Walls |
|---|---|
| Location | Taruhara 1161-3, Kamisaibara, Kagamino-cho, Tomata-gun, Okayama Prefecture |
| Designation | Registered Tangible Cultural Property (structure) |
| Year Designated | Registered 1930 structure on 2006-11-29 |
| Quantity | 1 site |
| Dimensions | Stone masonry, total length 90 metres |
| Owner | Chugoku Electric Power Co., Inc. |
| Public Access | Operating facility. Visible from the valley road; viewing of the plant by prior arrangement with the Tsuyama Power Office, 0868-27-0275 |
References
- National Cultural Properties Database, Agency for Cultural Affairs: Kamisaibara Power Station Penstock and Main Building Retaining Walls
- https://kunishitei.bunka.go.jp/heritage/detail/101/00006059
- Cultural Heritage Online, Agency for Cultural Affairs: Kamisaibara Power Station Penstock and Main Building Retaining Walls
- https://online.bunka.go.jp/heritages/detail/118934
- Okayama Prefecture, Cultural Properties Division: Registered Cultural Properties in Okayama Prefecture
- https://www.pref.okayama.jp/page/detail-50777.html
- Okayama Prefecture: Kamisaibara Power Station Facilities (PDF)
- https://www.pref.okayama.jp/uploaded/attachment/260992.pdf
- Okayama Prefecture: Iri Power Station Facilities (PDF)
- https://www.pref.okayama.jp/uploaded/attachment/260990.pdf
- Kagamino Town: Route buses and public transport
- https://www.town.kagamino.lg.jp/soshiki/22/2132.html
Last verified: 2026.09.08